Cationic aluminum alkyl complexes incorporating amidinate ligands as polymerization catalysts

ABSTRACT

Aluminum amidinate compounds of the formula   &lt;IMAGE&gt;   wherein R, R2, and R3 are selected from the group consisting of C1 to C50 alkyl, aryl, and silyl groups, X is an anionic ligand, preferably a hydrocarbyl, n=0 or 1, L, if present, is a labile Lewis base ligand, preferably having an oxygen, nitrogen, or phosphorus atom donating a lone pair of electrons to the aluminum center, and A- is an anion which balances the charge of the aluminum cation and only weakly if at all coordinates to the aluminum center and preferably contains boron, are disclosed. These compounds are useful as olefin polymerization catalysts without the need for cocatalysts or transition metal species.

BACKGROUND OF THE INVENTION

Ziegler-Natta type catalysts for polymerization of unsaturated hydrocarbons, such as alpha olefins, have long been the state of the art catalysts for such reactions. Typically, Ziegler-Natta type catalysts are composed of transition metal salts and aluminum alkyl compounds. While these catalysts are very effective and have a long-established record of use, they are not without drawbacks. For example, transition metals are expensive, potentially present some toxicity hazards, and to some are environmentally objectionable. Therefore, continuing efforts towards development of other suitable olefin polymerization catalysts have occurred. For example, metallocene catalysts have been developed for use in alpha olefin polymerization.

This invention has as its primary objective the development of catalysts for polymerization of unsaturated hydrocarbons which successfully polymerize without a transition metal moiety as part of the catalyst.

Another objective of the present invention is to prepare such catalysts in high yields and by use of convenient and practical synthetic methods.

A yet further objective of the present invention is a method of polymerizing unsaturated hydrocarbons using Ziegler-Natta like catalysts in the sense that the catalyst behaves similarly to Ziegler-Natta catalysts, but yet avoids the use of transition metals.

The method and manner of accomplishing each of the above objectives, as well as others, will become apparent from the detailed description of the invention which follows hereinafter.

SUMMARY OF THE INVENTION

The invention relates to novel catalysts, processes of synthesizing the catalysts, and to olefin polymerization reactions using the catalysts. The catalysts are cationic aluminum amidinate compounds. These compounds behave similarly to Ziegler-Natta catalysts, but avoid the use of transition metals.

DETAILED DESCRIPTION OF THE INVENTION

The formation of polyethylene from the reaction of neutral aluminum compounds including Cl₂ AlCH(Me)AlCl₂ or (AlR₃)₂ with ethylene in the temperature range 25 to 50° C. has been reported in Martin, H.; Bretinger, H. Makromol. Chem. 1992, 193, 1283. However, the reported catalytic activities are very low (1.6 ×10⁻¹ -3.8 ×10⁻⁴ g PE/(mol*h*atm)).

After extensive work with transition metal catalysts and investigation into the polymerization of unsaturated hydrocarbons such as olefins with a view to improving on the conventional processes by eliminating transition elements, a process has been discovered for polymerizing such unsaturated hydrocarbons with an entirely new class of catalyst compounds.

The catalysts are cationic aluminum amidinate compounds of the following formula: ##STR2## wherein R¹, R² and R³ are selected from the group consisting of C₁ to C₅₀ alkyl, aryl, or silyl groups, X is an anionic ligand, n=0 or 1, L is a labile Lewis base or donor ligand or a neutral aluminum species capable of coordination, and A⁻ is a counterbalancing non-coordinating or weakly coordinating anion.

The amidinate ligands (in anionic form) may be represented by structure C, which is the resonance hybrid of localized resonance structures A and B. Similarly, the base-free cationic aluminum complexes (n=b 0) may be represented by structure F, which is the resonance hybrid of localized resonance structures D and E. The situation for the base-stabilized cationic aluminum complexes (n=1) is analogous. ##STR3## In the above description of the resonance structures, R¹, R² and R³ are as earlier described. With regard to the invention, while they broadly can be C₁ to C₅₀, generally speaking, preferred R¹, R² and R³ groups are C₁ to C₁₂ alkyl, aryl or silyl.

The X moiety can represent a hydride radical, a dialkylamido radical, an alkoxide radical, an aryloxide radical, a hydrocarbyl radical, a substituted hydrocarbyl radical, a halocarbyl radical, or a thiolate radical. L is, of course, labile and can be displaced by other Lewis bases or donor ligands, including olefins, di-olefins, or any other unsaturated monomer.

The A⁻ moiety represents the non-coordinating or weakly coordinating counterbalancing anion. In particular, it represents a compatible, non-coordinating anion containing a single coordination complex comprising a charge-bearing metal or metalloid core which is relatively large (bulky), capable of stabilizing the active catalyst species and being sufficiently labile to be displaced by olefinic, di-olefinic or acetylenically unsaturated substrates, or other neutral Lewis bases or donor groups, such as ethers, nitrites and the like. Polyhedral borane anions, carborane anions and metallocarborane anions are also useful non-coordinating or weakly coordinating counterbalancing anions.

The key to proper anion design requires that the anionic complex is labile and stable toward reactions in the final catalyst species. Anions which are stable toward reactions with water or Bronsted acids and which do not have acidic protons located on the exterior of the anion (i.e. anionic complexes which do not react with strong acids or bases) possess the stability necessary to qualify as a stable anion for the catalyst system. The properties of the anion which are important for maximum lability include overall size, and shape (i.e. large radius of curvature), and nucleophilicity.

Using these guidelines one can use the chemical literature to choose non-coordinating anions which can serve as components in the catalyst system. In general, suitable anions for the second component may be any stable and bulky anionic complex having the following molecular attributes: 1) the anion should have a molecular diameter about or greater than 4 angstroms; 2) the anion should form stable salts with reducible Lewis Acids and protonated Lewis bases; 3) the negative charge on the anion should be delocalized over the framework of the anion or be localized within the core of the anion; 4) the anion should be a relatively poor nucleophile; and 5) the anion should not be a powerful reducing or oxidizing agent. Anions meeting these criteria--such as polynuclear boranes, carboranes, metallacarboranes, polyoxoanions and anionic coordination complexes are well described in the chemical literature.

Illustrative, but not limiting examples of non-coordinating or weakly coordinating counterbalancing anions are tetra(phenyl)borate, tetra(p-tolyl)borate, tetra(pentafluorophenyl)borate, tetra (3,5-bis-trifluoromethyl-phenyl)borate, (methyl)tris(pentafluorophenyl)borate, C₂ B₉ H₁₂ ⁻, CB₁₁ H₁₂ ⁻, B₁₂ H₁₂ ²⁻, and (C₂ B₉ H₁₁)₂ Co⁻.

As earlier stated, generally, these anions are (1) labile and can be displaced by an olefin, di-olefin or acetylenically unsaturated monomer, have a molecular diameter about or greater than 4 angstroms, form stable salts with reducible Lewis acids and protonated Lewis bases, have a negative charge delocalized over the framework on the anion of which the core thereof is not a reducing or oxidizing agent, and are relatively poor nucleophiles. For other examples of such counterbalancing, non-coordinating or weakly coordinating anions, see Strauss, S. H.; Chemical Reviews, 1993, 93, 927-942.

L, the optional labile Lewis base ligand, is also conventional and well known. It can, for example, be represented by tetrahydrofuran, ethers such as dimethyl ether, amines, alkyl amines, pyridine, substituted pyridines, and phosphines. L may also be represented by a neutral aluminum species which coordinates to the cation through a bridging group, such as {MeC(NPr^(i))₂ }AlMe₂ ; AlMe₃ ; and AlCl₃. The presence of such neutral coordinating ligands L is not critical, and they may or may not be present as deemed appropriate in any particular reaction.

The cationic aluminum amidinate complexes may be prepared by reacting a neutral precursor complex of the type {R² C(NR¹)(NR³)}AlX₂, where R¹, R², R³, and X are as defined above, with an activator compound which is capable of abstracting one X⁻ group from the precursor complex or of cleaving one Al--X bond of the precursor complex. Suitable activator compounds include Bronsted acids, such as ammonium salts, Lewis acids, such as AlCl₃ and B(C₆ F₅)₃, ionic reagents such as Ag⁺ and trityl salts, and oxidizing agents such as ferrocenium salts. Illustrative, but not limiting examples of suitable activator compounds are N,N-dimethylanilinium tetra(pentafluorophenyl)borate, methyldiphenylammonium tetra(pentafluorophenyl)borate, aluminum trichloride, tris(pentafluorophenyl)boron, silver (I) tetra(phenyl)borate, triphenylcarbenium tetra(pentafluorophenyl)borate, and ferrocenium tetra(phenyl)borate.

The synthesis of the catalyst compounds as earlier described for the present invention is particularly straightforward. Ideally, they are prepared on a high vacuum line under an inert atmosphere in the presence of solvents in the manner illustrated in the examples below. These examples of synthesis are illustrative and not intended to be limiting of the invention.

All manipulations were performed on a high-vacuum line or in a glove box under a purified N₂ atmosphere. Solvents were distilled from Na/benzophenone ketyl, except for chlorinated solvents, which were distilled from activated molecular sieves (3 Å) or P₂ O₅.

NMR spectra were recorded on a Bruker AMX 360 spectrometer in sealed or Teflon-valved tubes at ambient probe temperature unless otherwise indicated. ¹ H and ¹³ C chemical shifts are reported versus SiMe₄ and were determined by reference to the residual ¹ H and ¹³ C solvent peaks. All coupling constants are reported in Hz. The NMR spectra of cationic complexes contained resonances for B(C₆ F₅)₄ ⁻ or B(C₆ F₅)₃ Me!⁻.

NMR data for B(C₆ F₅)₄ ⁻ : ¹³ C NMR (CD₂ Cl₂): δ 148.6 (d,¹ J_(CF) =240.0 Hz), 138.7 (d,¹ J_(CF) =245.4 Hz), 136.8 (d,^(l) J_(CF) =245.4 Hz), 124.7 (br s, ipso-Ph). NMR data for MeB(C₆ F₅)₃ ⁻ : ¹ H NMR (CD₂ Cl₂): δ 0.47 (br s, 3H, B--CH₃). ¹³ C NMR (CD₂ Cl₂): δ 148.6 (d, ¹ J_(CF) =235.5 Hz), 137.9 (d,¹ J_(CF) =242.7 Hz), 136.8 (d,¹ J_(CF) =246.4 Hz), 129.7 (br s, ipso-Ph), 10.34 (br s, B--CH₃).

Mass spectra were obtained using the Direct Insertion Probe (DIP) method, on a VG Analytical Trio I instrument operating at 70 eV. Elemental analyses were performed by Desert Analytics Laboratory.

EXAMPLE 1 ({MeC(NPr^(i))₂ }AlMe₂)

A solution of 1,3-diisopropylcarbodimide (2.00 g, 10.7 mmol) in hexane (25 mL) was added dropwise via pipette to a rapidly stirred solution of AlMe₃ (1.06 mL, 11.0 mmol) in hexane (10 mL). An exothermic reactions was observed. The reaction mixture was stirred at room temperature for 18 h, after which time the volatiles were removed under vacuum affording pure {MeC(NPr^(i))₂ }AlMe₂ as a pale yellow liquid (2.30 g, 71%). ¹ H NMR (CD₂ Cl₂): δ 3.50 (sept,³ J_(HH) =6.3Hz, 2H, CHMe₂), 1.94 (s, 3H, CMe), 1.05 (d,³ J_(HH) =6.1 Hz, 12H, CHMe₂), -0.82 (s, 6H, AlMe₂). ¹³ C NMR (CD₂ Cl₂): δ 172.5 (s, CMe), 45.3 (d,¹ J_(CH) =132.2 Hz, CHMe₂), 25.3 (q, ¹ J_(CH=) 125.6 Hz, CHMe₂), 11.1 (q,¹ J_(CH) =128.3 Hz, CMe),-9.94 (br q), ¹ J_(CH) =114.1 Hz, AlMe₂). Anal. Calcd for C₁₀ H₂₃ N₂ Al: C, 60.57; H, 11.69; N, 14.13. Found: C, 60.41; H, 11.96; N, 14.50.

EXAMPLE 2 ({MeC(NCy)₂ }AlMe₂)

A solution of 1,3-dicyclohexylcarbodiimide (5.00 g, 24.2 mmol) in hexane (40 mL) was added slowly to a solution of AlMe₃ (2.40 mL, 25.0 mmol) in hexane (15 mL). The solution was stirred for 15 h and the volatiles were removed under vacuum yielding a pale yellow liquid that crystallized upon standing to afford pure {MeC(NCy)₂ }AlMe₂ as off-white crystals. (6.49 g, 93%). ¹ H NMR (CD₂ Cl₂): δ 3.10 (m, 2H, Cy), 1.92 (s, 3H, CMe), 1.69 (m,8H,Cy),1.56(m,2H,Cy), 1.35-1.06(m,8H+2H,Cy),-0.82(s,6H,AlMe₂). ¹³ C NMR (CD₂ Cl₂): δ 172.4(s,CMe), 53.0(d,¹ J_(CH) =131.4 Hz,Cy-C₁), 36.0(t,¹ J_(CH) =126.5 Hz,Cy), 26.1 (t,¹ J_(CH) =125.8 Hz,Cy), 25.4 (t,¹ J_(CH) =126.9 Hz,Cy), 11.2 (q,¹ J_(CH) =128.0 Hz, CMe),-9.78 (br q),¹ J_(CH) =112.6 Hz, AlMe₂). Anal. Calcd for C₁₆ H₃₁ N₂ Al: C, 69.02; H, 11.22; N, 10.06. Found: C, 68.88; H, 10.44; N, 10.15. Mass Spec. (EI, m/z): 263 M!⁺.

EXAMPLE 3 (Li Bu^(t) C(NPr^(i))₂ !)

A solution of 1,3-diisopropylcarbodimide (5.00 g, 39.6 mmol) in Et₂ O (50 mL) was cooled to 0° C. Bu^(t) Li(23.30 mL of a 1.7 M solution in pentane, 39.6 mmol) was added dropwise via syringe and the mixture was allowed to warm to room temperature. After 30 min the solvent was removed under vacuum affording a yellow oily solid which was dried under vacuum (18 h, 23° C.) to give a pale yellow solid. Trituration with hexane gave Li Bu^(t) C(NPr^(i))₂ ! as an off-white powder (4.56 g, 61%). ¹ H NMR (THF-d₈): δ 3.84 (sept, ³ J_(HH) =5.7 Hz, 2H, CHMe₂), 1.13 (s, 9H, CMe₃), 0.96 (d, ³ J_(HH) =6.1 Hz, 12H, CHMe₂). ¹³ C NMR (THF-d₈): δ 168.5 (s, CCMe₃), 46.6 (d, ¹ J_(CH) =122.3 Hz, CHMe₂), 39.4 (s, CMe₃), 31.0 (q,¹ J_(CH) =116.1 Hz, CHMe₂), 26.3 (q,¹ J_(CH) =116.1 Hz, CMe₃).

EXAMPLE 4 (Li Bu^(t) C(NCy)_(2!) )

A solution of 1,3-dicyclohexylcarbodimide (5.00 g, 24.2 mmol) in Et₂ O (50 mL) was cooled to 0° C. Bu^(t) Li (14.3 mL of a 1.7 M solution in pentane, 24.2 mmol) was added via syringe and the mixture was allowed to warm to room temperature. After 30 min the volatile components were removed under vacuum affording a yellow oily solid which was dried overnight under vacuum to yield a pale yellow powder. Trituration of this solid with pentane gave Li Bu^(t) C(NCy)₂ ! as a pale yellow powder (4.91 g, 75%). ¹ H NMR (THF-d₈): δ 3.50 (m,2H,Cy), 1.81-0.93 (m,20H,Cy), 1.10 (s,9H,CMe₃). ¹³ C NMR (THF-d₈): δ 168.3 (s,CCMe₃), 55.9 (d,¹ J_(CH) =119.8 Hz, Cy-C₁), 39.5 (s,CMe₃), 37.7 (t,¹ J_(CH) =118.9 Hz,Cy), 31.1 (q,¹ J_(CH) =117.7 Hz,CMe₃), 28.2 (t, partially obscured, Cy), 26.8 (t,¹ J_(CH) =119.4 Hz, Cy).

EXAMPLE 5 ({Bu^(t) C(NPr^(i))₂ }AlCl₂)

A solution of AlC1₃ (1.40 g, 10.5 mmol) in Et₂ O (30 mL) was cooled to -78° C. and added dropwise to a slurry of Li Bu^(t) C(NPr^(i))₂ ! (2.00 g, 10.5 mmol) in Et₂ O (50 mL) which was also at -78° C. The mixture was warmed to room temperature and stirred for 16 h, affording a slurry of a white solid in a yellow solution. The volatiles were removed under vacuum and the product was extracted from the LiCl with pentane. Concentration of the pentane extract and cooling to 0° C. afforded pure {Bu^(t) C(NPr^(i))₂ }AlCl₂ as opaque white crystals which were collected by filtration (2.01 g, 68%). ¹ H NMR (CD₂ Cl₂): δ 4.12 (br sept, ³ J_(HH) =5.9 Hz, 2H, CHMe₂), 1.43 (s,9H,CMe₃), 1.18 (d,³ J_(HH) =6.2 Hz, 12H, CHMe₂). ¹³ C NMR (CD₂ Cl₂): δ 184.3 (s, CCMe₃), 46.6 (d,¹ J_(CH) =135.7 Hz, CHMe₂), 40.1 (s,CMe₃), 29.2 (q,¹ J_(CH) =125.7 Hz, CMe₃), 25.9 (q,¹ J_(CH) =124.1 Hz, CHMe₂). Anal. Calcd for C₁₁ H₂₃ N₂ AlCl₂ : C, 46.98; H, 8.24; N, 9.96. Found: C, 46.84; H, 8.12; N, 9.85. Mass Spec. (EI,m/z,³⁵ Cl): 265 M!⁺.

EXAMPLE 6 ({Bu^(t) C(NCY)₂ }AlCl₂)

A solution of AlCl₃ (0.99 g, 7.4 mmol) in Et₂ O (25 mL) was added dropwise to a slurry of Li Bu^(t) C(NCy)₂ !(2.00 g, 7.4 mmol) in Et₂ O (50 mL) at -78° C. The mixture was warmed to room temperature and stirred for 18 h, affording a slurry of a white precipitate in a yellow solution. The volatiles were removed under vacuum and the product was extracted from the LiCl with toluene. Concentration of the toluene extract and cooling to 0° C. afforded pure {Bu^(t) (NCy)₂ }AlCl₂ as colorless crystals which were collected by filtration (1.84 g, 69%). ¹ H NMR (CD₂ Cl₂): δ 3.62 (br m,2H,Cy), 1.41 (s,9H,CMe₃), 1.91 -1.71 (m,4H,Cy), 1.62 (m,2H,Cy), 1.30-1.09 (m,8H+2H,Cy). ¹³ C NMR (CD₂ Cl₂): 67 184.4 (s,CCMe₃), 54.6 (d,¹ J_(CH) =138.7 Hz, Cy-C₁), 40.1 (s,CMe₃), 36.9 (t,¹ J_(CH) =127.9 Hz,Cy), 29.3 (q,¹ J_(CH) =127.7 Hz, CMe₃), 25.7 (t,¹ J_(CH) =125.7 Hz,Cy), 25.6 (t,¹ J_(CH) =125.7 Hz,Cy). Anal. Calcd for C₁₇ H₃₁ N₂ AlCl₂ : C, 56.51; H, 8.65; N, 7.75. Found: C, 56.22; H, 8.70; N, 7.67.

Mass Spec. (EI,m/z,³⁵ Cl):360 M!⁺.

EXAMPLE 7 ({BU^(t) C(NPr^(i))₂ }AlMe₂)

A solution of AlMe₂ Cl (0.25 mL, 2.7 mmol) in Et₂ O (25 mL) was added dropwise to a slurry of Li Bu^(t) C(NPr^(i))₂ !(0.50 g, 2.6 mmol) in Et₂ O (30 mL) at -78° C. The reaction mixture was allowed to warm slowly to room temperature and was stirred for 18 h. The volatiles were removed under vacuum and the residue was extracted with pentane. The extract was evaporated to dryness under vacuum yielding {Bu^(t) C(NPr^(i))₂ }AlMe₂ as a pale yellow solid (0.57 g, 87%). ¹ H NMR (CD₂ Cl₂): δ 4.07 (sept,³ J_(HH) =6.2 Hz,2H,CHMe₂), 1.38 (s,9H,CMe₃), 1.06 (d,³ J_(HH) =6.1 Hz,12H,CHMe₂), -0.81 (s,6H,AlMe₂). ¹³ C NMR (CD₂ Cl₂): 67 178.4 (s,CCMe₃), 45.8 (d,¹ J_(CH) =135.3 Hz,CHMe₂), 40.0 (s,CMe₃), 29.7 (q,¹ J_(CH) =127.0 Hz, CHMe₂), 26.3 (q,¹ J_(CH=) 125.5 Hz,CMe₃), -9.06 (br q,¹ J_(CH) =117.7 Hz,AlMe₂). Anal. Calcd for C₁₃ H₂₉ N₂ Al: C, 64.96; H, 12.16; N, 11.65. Found: C, 64.46; H, 11.90; N, 11.90. Mass Spec. (EI,m/z): 240 M!⁺, 225 M --CH₃ !⁺.

EXAMPLE 8 ({BU^(t) C(NCy)₂ }AlMe₂)

A solution of AlMe₂ Cl (0.71 mL, 7.7 mmol) in Et₂ O (30 mL) was added dropwise to a slurry of Li Bu^(t) C(NCy)₂ ! (2.00 g, 7.4 mmol) in Et₂ O (40 mL) at -78° C. The mixture was allowed to warm to room temperature and was stirred for 15 h. The volatiles were removed under vacuum and the residue was extracted with pentane (3×15 mL). The extract was concentrated to 30 mL and maintained at room temperature affording {Bu^(t) C(NCy)₂ }AlMe₂ (2.00 g, 83%) as large colorless crystals which were collected by filtration.¹ H NMR (CD₂ Cl₂): δ 3.56 (m,2H,Cy), 1.80-1.69 (m,8H,Cy), 1.61-1.57 (m,2H,Cy), 1.36 (s,9H,CMe₃), 1.27-1.03 (m,8H+2H,Cy), -0.83 (s,6H,ALMe₂). ¹³ C NMR (CD₂ Cl₂): δ 178.5 (s,CCMe₃), 54.2 (d,¹ J_(CH) =125.9 Hz, Cy-C₁), 39.9 (s,CMe₃), 37.3 (t,¹ J_(CH) =119.3 Hz,Cy), 29.7 (q,¹ J_(CH) =117.3 Hz,CMe₃), 26.1 (t,¹ J_(CH) =119.3 Hz,Cy), 26.0 (t,¹ J_(CH) =119.3 Hz, Cy), -9.1 (br q,¹ J_(CH) =103.9 Hz,AlMe₂). Anal. Calcd for C₁₉ H₃₇ N₂ Al: C, 71.20; H, 11.64; N, 8.74. Found: C, 71.18; H, 11.88; N. 8.73. Mass Spec. (EI,m/z): 320 M!⁺, 305 M--CH₃ !⁺.

EXAMPLE 9 ({Bu^(t) C(NPr^(i))₂ }Al(CH₂ Ph)₂)

A solution of {Bu^(t) C(NPr^(i))₂ }AlCl₂ (0.50 g, 1.8 mmol) in Et₂ O (25 mL) was cooled to -78° C. and PhCH₂ MgCl (3.56 mL of a 1.0 M solution in Et₂ O, 3.6 mmol) was added dropwise via syringe. The reaction mixture was allowed to warm to room temperature and was stirred for 15 h. The volatiles were removed under vacuum and the residue was extracted with pentane. The extract was evaporated to dryness under vacuum affording pure {Bu^(t) C(NPr^(i))₂ }Al(CH₂ Ph)₂ as a viscous oil (0.55 g, 79%) that can be induced to solidify through storage at -40° C. ¹ H NMR (CD₂ Cl₂): δ 7.11 (t,³ J_(HH) =7.6 Hz,4H,m-Ph), 7.02 (d,³ J_(HH) =6.9 Hz,4H,o-Ph), 6.88 (t,³ J_(HH) =7.3 Hz,2H,p-Ph), 4.00 (sept,³ J_(HH) =6.2 Hz,2H,CHMe₂), 1.75 (s,4H,CH₂ Ph), 1.34 (s,9H,CMe₃), 0.94 (d,³ J_(HH) =6.2 Hz, 12H, CHMe₂). ¹³ C NMR (CD₂ Cl₂): δ 180.8 (s,CCMe₃), 146.8 (s,ipso-Ph), 128.2 (d,¹ J_(CH) =155.8 Hz, o- or m-Ph), 127.5 (d,¹ J_(CH) =149.4 Hz, o- or m-Ph), 121.7 (d,¹ J_(CH) =148.5 Hz,p-Ph), 45.6 (d,¹ J_(CH) =128.9 Hz,CHMe₂), 40.1 (s,CMe₃), 29.6 (q,¹ J_(CH) =119.0 Hz,CMe₃), 26.3 (q,¹ J_(CH) =116.4 Hz,CHMe₂), 21.4 (br t,¹ J_(CH) =108.9 Hz, CH₂ Ph). Anal. Calcd for C₂₅ H₃₇ N₂ Al: C, 76.49; H, 9.50; N, 7.14. Found: C, 75.05; H, 9.63; N, 6.89. Mass Spec. (EI,mlz): 301 M--CH₂ Ph!⁺.

EXAMPLE 10 ({Bu^(t) C(NCy)₂ }Al(CH₂ Ph)₂)

A solution of {Bu^(t) C(NCy)₂ }AlCl₂ (0.50 g, 1.4 mmol) in Et₂ O (20 mL) was cooled to -78° C. and PhCH₂ MgCl (2.76 mL of a 1.0 M solution in Et₂ O, 2.8 mmol) was added dropwise by syringe. The mixture was allowed to warm slowly to room temperature and was stirred for 15 h. The volatiles were removed under vacuum and the residue was extracted with pentane. The extract was evaporated under vacuum affording pure {Bu^(t) C(NCy)₂ }Al(CH₂ Ph)₂ as a viscous white oil. (0.57 g, 87%). ¹ H NMR (CD₂ Cl₂): δ 7.08 (t,³ J_(HH) =7.6 Hz,4H,m-Ph), 6.98 (d,³ JHH=6.9 Hz,4H,o-Ph), 6.84 (t,³ JHH=⁷.³ Hz,2H,p-Ph), 3.44 (m,2H,Cy), 1.69 (s,4H,CH₂ Ph), 1.63-1.51 (m,4H+2H,Cy), 1.27 (s,9H,CMe₃), 1.21-0.78 (m,14H,Cy). ¹³ C NMR (CD₂ Cl₂): 6 180.8 (s,CCMe₃), 146.9 (s,ipso-Ph), 126.2 (d,¹ J_(CH) =155.8 Hz, o- or m-Ph), 127.5 (d,¹ J_(CH) =147.6 Hz, o- or m-Ph), 121.6 (d,JCH=151.³ Hz,p-Ph), 54.0 (d, partially obscured, Cy-C₁), 40.0 (s,CMe₃), 37.1 (t,¹ J_(CH) =117.7 Hz,Cy), 29.6 (q,¹ J_(CH) =117.3 Hz,CMe₃), 25.9 (t,¹ JCH=118.2 Hz,Cy), 25.7 (t,¹ JCH=¹¹⁸.² Hz,Cy), 21.4 (t,¹ J_(CH) =108.7 Hz,CH₂ Ph). Anal. Calcd for C₃₁ H₄₅ N₂ Al: C, 78.77; H, 9.60; N, 5.93. Found: C, 78.62; H,9.58; N, 5.83.

EXAMPLE 11 ({Bu^(t) C(NPr^(i))₂ }Al(CH₂ CMe₃)₂)

{Bu^(t) C(NPr^(i))₂ }AlCl₂ (0.50 g, 1.8 mmol) and LiCH₂ CMe₃ (0.28 g, 3.6 mmol) were mixed as solids in the glove box.

Et₂ O (40 mL) was added at -78° C. and the mixture was allowed to warm slowly to room temperature, affording a colorless solution and a white precipitate. The mixture was stirred for 18 h and the volatiles were removed under vacuum. The residue was extracted with pentane (3×10 mL). The extract was taken to dryness under vacuum affording {Bu^(t) C(NiPr)₂ }Al(CH₂ CMe₃)₂ as a white solid (0.58 g, 93%). ¹ H NMR (CD₂ Cl₂): δ 4.13 (sept,³ J_(HH) =6.2 Hz, CHMe₂), 1.39 (s,9H,CMe₃), 1.15 (d,³ J_(HH) =6.3 Hz, CHMe₂), 0.99 (s,18H,CH₂ CMe₃), 0.27 (s,4H,CH₂ CMe₃). ¹³ C NMR (CD₂ Cl₂): δ179.7 (s,CCMe₃), 46.1 (d,¹ J_(CH) =121.0 Hz,CHMe₂), 40.1 (s,CMe₃), 35.2 (q,¹ J_(CH) =112.2 Hz, CH₂ CMe₃), 32.1 (br t, partially obscured, CH₂ CMe₃), 31.6 (s, CH₂ CMe₃), 29.8 (q,¹ J_(CH) =121.2 Hz,CMe₃), 26.6 (q,¹ J_(CH) =117.9 Hz, CHMe₂). Anal. Calcd for C₂₁ H₄₅ N₂ Al: C, 71.54; H, 12.86; N, 7.95. Found: C, 70.46; H, 12.82; N, 7.72. Mass Spec. (EI,m/z): 281 M--CH₂ CMe₃ !⁺.

EXAMPLE 12 ({Bu^(t) C(NCy)₂ }Al(CH₂ CMe₃)₂)

A solution of LiCH₂ CMe₃ (0.43 g, 5.5 mmol) in Et₂ O (20 mL) was added dropwise at -78° C. to an Et₂ O solution (30 mL) of {Bu^(t) C(NCy)₂ }AlCl₂ (1.00 g, 2.8 mmol). The reaction mixture was allowed to warm slowly to room temperature and was stirred for 15 h. The volatiles were removed under vacuum and the residue was extracted with pentane. The extract was evaporated to dryness under vacuum to afford pure {Bu^(t) C(NCy)₂ }Al(CH₂ CMe₃)₂ as a white solid material (1.13 g, 94%). ¹ H NMR (CD₂ Cl₂): δ 3.63 (m,2H,Cy), 1.86-1.71 (m,8H,Cy), 1.60 (m,2H,Cy), 1.36 (s,9H,CMe₃), 1.30-1.09 (m,8H+2H,Cy), 0.99 (s,CH₂ CMe₃), 0.25 (s,4H,CH₂ CMe₃). ¹³ C NMR (CD₂ Cl₂): δ 179.7 (s,CCMe₃), 54.8 (d,¹ J_(CH) =126.8 Hz, Cy-C_(l)), 40.0 (s,CMe₃), 37.2 (t,¹ J_(CH) =124.3 Hz,Cy), 35.2 (q,¹ J_(CH) =117.6 Hz, CH₂ CMe₃), 32.1 (br t, partially obscured, CH₂ CMe₃), 31.6 (s,CH₂ CMe₃), 29.8 (q,¹ J_(CH) =119.6 Hz, CMe₃), 26.2 (t¹ J_(CH) =118.2 Hz, Cy), 26.1 (t,¹ J_(CH) =118.2 Hz, Cy). Anal. Calcd for C-₂₇ H₅₃ N₂ Al: C, 74.95; H, 12.35; N, 6.47. Found: C, 73.87; H, 12.42; N, 6.60. Mass Spec. (EI,m/z): 362 M--CH₂ CMe₃ !⁺.

EXAMPLE 13 ( ({MeC(NPr^(i))₂ }AlMe)₂ (μ-Me)! MeB(C₆ F₅)₃ !

A solution of B(C₆ F₅)₃ (0.77 g, 1.5 mmol) in CH₂ Cl₂ (20 mL) was added to {MeC(NPr^(i))₂ }AlMe₂ (0.60 g, 3.0 mmol) also in CH₂ C1₂ (15 mL). The reaction mixture was allowed to stir for 30 min at room temperature and the volatiles were removed under vacuum leaving an oily white solid. Trituration with pentane afforded ({MeC(NPr^(i))₂ }AlMe)₂ (μ-Me)! MeB(C₆ F₅)₃ ! as a white powder (0.91 g, 83%). ¹ H NMR (CD₂ C1₂, 293 K): δ 3.79 (sept,³ J_(HH) =6.6 Hz,4H,CHMe₂), 2.31 (s,6H,CMe), 1.28 (d,³ J_(HH) =6.5 Hz,24H,CHMe₂), -0.38 (br s,9H,AlMe). ¹ H NMR (CD₂ Cl₂, 193K): δ 3.79 (br sept,2H,CHMe₂), 3.67 (br sept,6H,CHMe₂), 2.33 (s,6H,CMe), 2.15 (s,6H,CMe), 1.30 (m,18H,CHMe₂), 1.18 (m,12H,CHMe₂), 1.02 (m,18H,CHMe₂), -0.17 (s, 6H, AlMe), -0.54 (s, 6H, Al-Me), -0.75 (s, 6H, AlMe). ¹¹ B NMR (CD₂ Cl₂): δ -13.4 (br s, MeB(C₆ F₅)₃). ¹³ C NMR (CD₂ Cl₂): δ 182.0 (s,CMe), 50.5 (d,¹ J_(CH) =138.9 Hz, CHMe₂), 23.4 (q,¹ J_(CH) =127.0 Hz, CHMe₂), 17.8 (q,¹ J_(CH) =130.3 Hz, CMe), -5.6 (br q,¹ J_(CH) =130.3 Hz, AlMe). Anal. Calcd for C₃₈ H₄₆ N₄ A1₂ BF₁₅ : C, 50.23; H, 5.10; N, 6.17. Found: C, 50.46; H, 4.92; N, 6.09.

EXAMPLE 14 ( {MeC(NPr^(i))₂ }AlMe(NMe₂ Ph)! B(C₆ F₅)₄ !)

A CD₂ Cl₂ solution (600 μL) of HNMe₂ Ph! B(C₆ F₅)4 ! (85.3 mg, 0.11 mmol) was added to a vial containing {MeC(NPr^(i))₂ }AlMe₂ (21.1 mg, 0.11 mmol). The mixture was transferred to an NMR tube and NMR spectra were recorded showing complete conversion to {MeC(NPr^(i))₂ }AlMe(NMe₂ Ph)! B(C₆ F₅) 4 !. ¹ H NMR (CD₂ Cl_(2:) δ 7.63 (t,³ J_(HH) =7.9 Hz,2H,m-Ph), 7.51 (t,³ J_(HH) =7.3 Hz,lH,p-Ph), 7.47 (d,³ J_(HH) =7.9 Hz,2H,o-Ph), 3.58 (sept,³ J_(HH) =6.4 Hz, 2H,CHMe₂), 3.20 (s, 6H, NMe₂ Ph), 2.17 (s, 3H, CMe), 1.03 (d,³ J_(HH) =6.5 Hz, 6H, CHMe₂), 0.92 (d,³ J_(HH) =6.4 Hz, 6H, CHMe₂), -0.30 (s, 3H, AlMe). ¹³ C NMR (CD₂ Cl₂): δ 182.0 (s,CMe), 143.7 (s, ipso-Ph), 131.4 (d,¹ J_(CH) =159.4 Hz, o-Ph), 129.8 (d,¹ J_(CH) =164.8 Hz, p-Ph), 120.9 (d,¹ J_(CH) =153.1 Hz, m-Ph), 46.7 (q,¹ J_(CH) =134.7 Hz, NMe₂), 46.0 (d,¹ J_(CH) =125.2 Hz, CHMe₂), 24.7 (q,¹ J_(CH) =119. Hz, CHMe₂), 24.6 (q,¹ J_(CH) =119.7 Hz, CHMe₂), 12.7 (q,¹ J_(CH) =122.6 Hz, CMe), -13.4 (br q,¹ J_(CH) =116.8 Hz, ALMe).

EXAMPLE 15 ( {MeC(NPr^(i))₂ }AlMe(PMe₃)! MeB(C₆ F₅)₃ !

A CD₂ C1₂ solution of ({MeC(NPr^(i))₂ }AlMe)₂ (μ-Me)! MeB(C₆ F₅)₃ ! was cooled in liquid N₂ and PMe₃ (5 equiv) was condensed onto the frozen solution. The mixture was warmed to room temperature and the ¹ H NMR spectrum was recorded, showing that complete formation of the trimethylphosphine adduct {MeC(NPr^(i))₂ }AlMe(PMe₃)! MeB(C₆ F₅)₃ ! and {MeC(NPr^(i))₂ }AlMe₂ had occurred. To obtain a sample free from reaction byproducts, the NMR tube was evacuated and pumped on for 18 h. The resulting oily solid was redissolved in CD₂ CI₂ and the NMR spectra was recorded, and showed that only {MeC(NPr^(i))₂ }AlMe(PMe₃)! MeB(C₆ F₅)₃ ! was present. ¹ H NMR (CD₂ Cl₂): δ 3.62 (sept,³ J_(HH) =6.3 Hz, 2H, CHMe₂), 2.17 (s, 3H, CMe), 1.52 (d,² J_(PC) =9.4 Hz, 9H, PMe₃), 1.10 (d,³ J_(HH) =6.3 Hz, 12H, CHMe₂), -0.27 (s, 3H, AlMe). ³¹ p NMR (CD₂ Cl₂): δ -34.55 (s,PMe₃). ¹³ C NMR (CD₂ Cl₂): δ 180.6 (s, CMe), 45.5 (d,¹ J_(CH) =131.1 Hz, CHMe₂), 25.3 (q,¹ J_(CH) =121.0 Hz, CHMe₂), 12.4 (q,¹ J_(CH) =124.7 Hz, CMe), 9.1 (dq,¹ J_(PC=) 29.6 Hz,¹ J_(CH) =127.6 Hz, PMe₃), -12.8 (br q,¹ J_(CH) =109.6 Hz, AlMe).

EXAMPLE 16 ( {MeC(NPr^(i))₂ }AlMe(PMe₃)! B(C₆ F₅)₄ !)

A CD₂ Cl₂ solution of {MeC(NPr^(i))₂ }AlMe(NMe₂ Ph)! B(C₆ F₅)₄ ! was cooled in liquid N₂ and PMe₃ (5 equiv) was condensed onto the frozen solution. The mixture was warmed to room temperature and the ¹ H NMR spectrum was recorded, showing that formation of the trimethylphosphine adduct {MeC(NPr^(i))₂ }AlMe(PMe₃)! B(C₆ F₅)4! and free NMe₂ Ph had occurred. 1H NMR (CD₂ Cl₂): δ 3.62 (sept, ³ J_(HH) =6.3 Hz, 2H, CHMe₂), 2.17 (s, 3H, CMe), 1.52 (d, ² J_(PC=) 9.4 Hz, 9H, PMe₃), 1.10 (d,³ J_(HH) =6.3 Hz, 12H, CHMe₂), -0.27 (s, 3H, AlMe). 31P NMR (CD₂ Cl_(2:) δ -34.55 (s, PMe₃). ¹³ C NMR (CD₂ Cl₂): δ 180.6 (s, CMe), 45.5 (d,¹ J_(CH) =131.1 Hz, CHMe₂), 25.3 (q,¹ J_(CH) =121.0 Hz, CHMe₂), 12.4 (q,¹ J_(CH) =124.7 Hz, CMe), 9.1 (dq,¹ J_(PC) =29.6 Hz, ¹ J_(CH) =127.6 Hz, PMe₃), -12.8 (br q,¹ J_(CH) =109.6 Hz, AlMe).

Based upon the above synthesis illustration Examples 1-16, it can be seen that the cationic aluminum alkyl complexes are prepared by reacting a neutral precursor complex of the type R² C(NR¹)(NR³)AlX₂, where R¹, R², R³ and X are as defined above, with an activator compound which is capable of abstracting one X- group from the precursor complex or of cleaving one Al--X bond of the precursor complex. Additionally, example 15 shows that the {MeC(NPr^(i))₂ }AlMe₂ moiety of ({MeC(NPr^(i))₂ }AlMe)₂ (μ-Me! MeB(C₆ F₅) 3 ! can be displaced by the Lewis base PMe₃, and example 16 shows that the NMe₂ Ph group of {MeC(NPr^(i))₂ }AlMe(NMe₂ Ph)! B(C₆ F₅)₄ ! can be displaced by PMe₃.

The following two additional examples illustrate the preparation of base-free cations.

EXAMPLE 17 ( {(Bu^(t) C(NPr^(i))₂ }AlMe! MeB(C₆ F₅)₃ !)

A solution of {Bu^(t) C(NPr^(i))₂ }AlMe₂ (0.040 g, 0.17 mmol) in toluene (1.5 cm³) was prepared in the dry box. This was added dropwise via pipette to a solution of 1 equiv B(C₆ F₅)₃ (0.087 g, 0.17 mmol) also in toluene (2.5 cm³) that was rapidly stirring in an ampoule fitted with a teflon tap. The ampoule was sealed and the mixture was removed from the dry box and stirred on a vacuum line for 30 mins. The volatiles were then removed under reduced pressure, leaving an off-white, oily residue. (CD₂ C1)₂ was added to this residue and the solution transferred to an NMR tube. The ¹ H NMR spectrum was recorded immediately and showed complete conversion to the desired base-free cation {Bu^(t) C(NPr^(i))₂ }AlMe! MeB(C₆ F₅)₃ !. ¹ H NMR (CD₂ Cl)_(2:) δ 4.12 (sept,³ J_(HH) =6.2 Hz, 2H, CHMe₂), 1.67 (br s, 3H, BCH₃), 1.42 (s, 9H, CMe₃), 1.09 (d,³ J_(HH) =6.2 Hz, CHMe₂), 0.96 (d,³ J_(HH) =6.2 Hz, CHMe₂), -0.44 (br s, 3H, AlMe). ¹³ C NMR (CD₂ Cl)_(2:) δ 181.3 (s, CCMe₃), 46.0 (d,¹ J_(CH) =132.1 Hz, CHMe₂), 40.1 (s, CMe₃), 29.3 (q,¹ J_(CH) =122.3 Hz, CMe₃), 26.4 (q,¹ J_(CH) =125.3 Hz, CHMe₂), 25.5 (q,¹ J_(CH) =121.2 Hz, CHMe₂), -8.7 (br q,¹ J_(CH) =118.1 Hz, AlMe).

EXAMPLE 18 ( {Bu^(t) C(NCy)₂ }AlMe! MeB(C₆ F₅)₃ !)

The product was prepared in an identical manner to that outlined above, using 0.033 g {Bu^(t) C(NCy)₂ }AlMe₂ (0.10 mmol) and 0.053 g B(C₆ F₅)₃ (1 equiv, 0.10 mmol). Again 100% conversion to the base-free cation was observed. ¹ H NMR (CD₂ Cl)_(2:) δ 3.61 (m, 2H, Cy), 1.83-1.74 (br m, 4H, Cy), 1.66 (br s, 3H, BCH₃), 1.55 (br t, 4H, Cy), 1.37 (s, 9H, CMe₃), 1.25-0.98 (m, 8H, Cy), 0.89-0.79 (m, 4H, Cy), -0.46 (s, 3H, AlMe). ¹³ C NMR (CD₂ Cl)_(2:) δ 181.1 (s, CCMe₃), 54.1 (d,¹ J_(CH) =134.0 Hz, Cy-C₁), 39.9 (s, CMe₃), 37.5 (t,¹ J_(CH) =129.0 Hz, Cy), 36.6 (t,¹ J_(CH) =126.2 Hz, Cy), 29.3 (q,¹ J_(CH) =122.3 Hz, CMe₃), 25.8 (t,¹ J_(CH) =122.5 Hz, Cy), -8.5 (q,¹ J_(CH) =114.7 Hz, AlMe).

EXAMPLE 19 (Polymerization Procedure for Ethylene)

All polymerizations were carried out using transition metal-free conditions, employing glass apparatus and Teflon-coated stirrer bars. In a typical experiment, 0.02 g of {Bu^(t) C(NPr^(i))₂ }AlMe₂ was weighed out into a glass vial in the dry box, and 3 mL of dry toluene was added. 1 equiv of activator, based on the aluminum compound was weighed into a Fischer-Porter bottle and ca. 50 cm³ of toluene was added. The aluminum complex solution was added dropwise over 2 minutes (using a pipette) to the rapidly stirring activator solution, ensuring efficient mixing of the 2 components, and a constant excess of activator (to limit formation of base adduct species). The apparatus was then removed from the dry box and connected to the polymerization equipment, consisting of an ethylene cylinder, metal vacuum line and gas purification system. This had been previously evacuated to remove any residual gas from the system. The mixture was allowed to equilibrate at the temperature required for the experiment (10-20 minutes) before the introduction of ethylene (Note, the Fischer-Porter bottle was placed under slight vacuum prior to introduction of the ethylene, to reduce the nitrogen content within and maximize ethylene dissolution in the solvent). The polymerization was typically allowed to run for 60 minutes, after which time the ethylene flow to the system was halted. The apparatus was vented in a fume hood and disassembled. 50-80 mL of a mixture of methanol (ca. 150 mL) and conc. HCl (ca. 1.5 mL) was added to the solution to quench the reaction and the precipitate (if any) was collected by filtration. The polymer was then washed with acidified water (ca. 1.5 mL conc. HC1 in 100 mL H₂ 0) to ensure removal of the Al-salts, dried in a vacuum oven at 60° C. for 2-8 hours. The weight recorded and the activity calculated (see table).

The results of the ethylene polymerizations are arized in the table below.

    ______________________________________                                         Table of Results for Ethylene Polymerization                                   (neutral precursor complex = {Bu.sup.t C (NPr.sup.i).sub.2 } AlMe.sub.2;       ethylene pressure = 2 atm; solvent = toluene)                                                                         Activity                                     Activator     Time    Temp Yield PE                                                                              (g PE/mol                               Run  Compound      (mins)  (°C.)                                                                        (g)    cat/hr/atm)                             ______________________________________                                         1    B(C.sub.6 F.sub.5).sub.3                                                                     60      26   0.053  293                                     2    B(C.sub.6 F.sub.5).sub.3                                                                     60      60   0.115  697                                     3    B(C.sub.6 F.sub.5).sub.3                                                                     60      85   0.026  162                                     4     Ph.sub.3 C!  B(C.sub.6 F.sub.5).sub.4 !                                                     60      26   0.084  530                                     5     Ph.sub.3 C!  B(C.sub.6 F.sub.5).sub.4 !                                                     60      60   0.293  1177                                    6     Ph.sub.3 C!  B(C.sub.6 F.sub.5).sub.4 !                                                      30*    60   0.266  3183                                    7     Ph.sub.3 C!  B(C.sub.6 F.sub.5).sub.4 !                                                      30*    85   0.351  4145                                    ______________________________________                                          (* = solution stopped stirring due to precipitate forming therefore            stopped after 30 mins)                                                   

As can be seen from the above, effective catalysts for alpha-olefin polymerizations in particular are prepared that avoid any transition metals. It therefore can be seen that the invention accomplishes at least all of its stated objectives. 

What is claimed is:
 1. Aluminum amidinate compounds of the formula: ##STR4## wherein R¹, R², and R³ are selected from the group consisting of C₁ to C₅₀ alkyl, aryl and silyl groups, X is an anionic ligand, n=0 or 1, L, if present, is a labile Lewis-base or donor ligand, and A⁻ is a counterbalancing non-coordinating or weakly coordinating anion.
 2. A compound of claim 1 wherein R¹, R² and R³ are selected from the group consisting of C₁ to C₁₂ alkyl, aryl and silyl groups.
 3. A compound of claim 1 wherein X is hydride, dialkylamido, alkoxide, aryloxide, hydrocarbyl, halocarbyl, or thiolate.
 4. A compound of claim 1 wherein L, if present, is selected from the group consisting of tetrahydrofuran, ethers, amines, alkylamines, pyridine and phosphines.
 5. A compound of claim 1 wherein A⁻ is a boron containing anion.
 6. The process of synthesizing cationic aluminum compounds, comprising:reacting a neutral precursor complex of the formula {R² C(NR¹)(NR³)}AlX₂ wherein R¹, R², and R³ are selected from the group consisting of C₁ to C₅₀ alkyl, aryl, and silyl groups, with an activator compound that will either abstract an X⁻ moiety from the precursor complex or cleave an Al--X bond.
 7. The process of claim 6 wherein R¹, R², and R³ are selected from the group consisting of C₁ to C₁₂ alkyl, aryl, and silyl groups.
 8. The process of claim 6 wherein X is a hydride, dialkyl amido, alkoxide, aryloxide, hydrocarbyl, halo-carbyl or thiolate. 